A color electrophotographic image forming apparatus using a rotatable supporting member (rotary) which supports a plurality of developing devices has been conventionally known. In the image forming apparatus, by rotating the rotatable supporting member, any of the plurality of developing devices supported by the rotatable supporting member is successively moved to a developing position where the rotatable supporting member opposes a photosensitive drum. The developing device moved to the developing position is engaged with an electric energy supplying means and a drive transmitting means which are provided in an apparatus main assembly (of the image forming apparatus), so that electric energy supply and driving force transmission are effected (e.g., Japanese Laid-Open Patent Application 2008-310302). Then, by the developing device moved to the developing position, development of an electrostatic latent image formed on the photosensitive drum is effected.
In general, in a constitution using the above-described rotatable supporting member, from the viewpoint of operational stability, a gap with respect to a thrust direction is provided between the rotatable supporting member and the apparatus main assembly which supports the rotatable supporting member. The reason therefor is that when there is no sufficient gap in the case where a dimension with respect to the thrust direction is increased due to component tolerance or thermal expansion, the rotatable supporting member strongly urges against and interferes with the apparatus main assembly and thus there is a possibility that the rotatable supporting member constitutes a hindrance to rotation thereof. Further, in a constitution of the electric energy supply and drive transmission to the developing device, there is a need to constitute the rotatable supporting member with a width with respect to the thrust direction including the above-described gap.
However, in recent years, downsizing of the color electrophotographic image forming apparatus is advanced and with the downsizing of the apparatus, a size of the apparatus with respect to the thrust direction is also decreased, so that when the sufficient gap as described above is ensured, there is a problem that the downsizing of the apparatus is not readily realized.